1. Field of the Invention
This invention relates to the manufacture and composition of gear oil additives used to decrease the corrosion of yellow metal components which are present in axles and transmissions. This corrosion may occur from the use of sulfurized olefins in the gear oil.
2. Background
In gear oil applications, sulfurized olefins are typically used to protect gears from scoring. However, these sulfur compounds are extremely corrosive towards yellow metals, such as copper and copper alloys. The sulfur components in combination with phosphorus components produce a composition that degrades the copper. Gear oil specifications have minimum requirements for copper corrosion. For example, API GL-5 category requires a maximum rating of 3 in the ASTM D-130 test. Typically, to decrease copper corrosion, copper passivators, such as thiadiazoles and triazoles, are added in enough quantities until the lubricating oil has an acceptable copper corrosion performance. The addition of copper passivators is costly. Therefore, a new, cost efficient gear oil additive has been discovered that decreases copper corrosion as well as decreases the cost of the gear oil additive.
Van Der Veer et al., International Publication Number WO 98/16669, disclose a corrosion inhibiting composition that comprises at least (A) a carrier of an oily or waxy type; and (B) active components comprising at least (B1) a corrosion-inhibitor of the azole-type, and (B2) a co-corrision-inhibitior, selected from the group consisting of (a) aromatic acids and naphthenic acids, which acids have the free acid form or the alkaline, alkaline earth, ammonium and/or amine salt form, with the proviso that sodium benzoate is excluded, (b) imidazoline derivatives having a C6-24 alkyl moiety, and (c) C6-24 alkyl and alkenyl succinic acids including the anhydride compounds thereof, as well as mixtures of compounds defined under (a), (b) and/or (c). Typically, this component is used to decrease the corrosion of elongated objects of steel.
Junga, International Publication Number WO 94/17164, discloses an anti-wear, high pressure hydraulic oil which contains essentially no zinc or phosphorus. The hydraulic oil protects against corrosion and oxidation as well as provides anti-wear, anti-weld, and demulsibility properties. The hydraulic oil contains (1) petroleum hydrocarbon oil; (2) esters of dibasic and monobasic acids; (3) butylated phenol; (4) phenol; (5) sulfurized fatty oil; (6) fatty acid; and (7) sulfur scavenger.
Baumgart et al., U.S. Pat. No. 6,413,916, disclose a lubricant composition that deposits a corrosion protective coating on the surface which prevents corrosion and reduces wear. The composition comprises a light mineral oil of high purity, a molybdenum based lubricant, a metal sulfonate such as calcium sulfonate, a long chain fatty acid, ZDP, a zinc dithiophosphate derivative and more particularly a zinc alkyldithiophosphate, or diazole such as thiadiazole derivative.
Khorramian, U.S. Pat. No. 5,439,605, discloses a base oil that contains a copper passivator. The copper passivator is preferably a benzotriazole derivative such as 1H-benzotriazole-1-Methanamine,N,N-bis(2-ethyl hexyl)-methyl; and the copper passivator is preferably present in the final zinc dialkyldithiophosphate (ZDTP)-free, with or without phosphorus, low ash or light ash lubricating oil.
Newingham et al., U.S. Pat. No. 3,923,669, disclose an anti-wear hydraulic oil that comprises major amounts of a mineral lubricating oil and minor amounts of a secondary zinc dialkyl dithiophosphate anti-wear agent, chelating type and film forming type metal deactivators, a neutral barium salt of a petroleum sulfonate, and a succinic acid based rust inhibitor.
Taguchi et al., European Patent Application No. EP 0926 224 A2, disclose the addition of a compound which is composed of at least one cyclic dicarboxylic acid anhydride substituted by one or more specific alkyl or alkenyl groups, in an effective proportion to a lubricating base stock. The addition of this compound provides a lubricating oil composition for an automatic or continuously variable transmission which achieves a sufficient friction coefficient in a high sliding speed range while retaining lubricating oil properties required as a lubricating oil for the automatic or continuously variable transmission.